Papers by Author: Hua Xiao

Abstract: Antibiotics are used in large amounts as human and veterinary medicine. Due to their use pattern, they possess a potential for reaching the water environment. In recent years great amount of evidence showed that tetracycline antibiotics were frequently detected in aquatic environment. In this paper, the literature on adsorption of tetracyclines (TCs) were reviewed and summarized. Adsorption kinetics, adsorption isotherm, and adsorption mechanism were discussed. The pseudo-second-order kinetics model fit the experimental data best in most cases of adsorption of TCs. Sorption of TCs followed Freundlich or Langmuir isotherm well in all cases. At last, main adsorption mechanisms such as cation exchange, cation bridging at surfaces, surface complexation, and hydrogen bonding could be suggested based on analysis by XRD, FTIR, NMR, HPLC, LC-MS, etc.

Abstract: Hydrotalcites (HT-X) of different Mg/Al ratio (X is Mg/Al molar ratio, 3 and 4) was synthesized by co-precipitation method. Calcined HTLCs (CHT-X) at 500°C have been shown to recover their original layered structure by taking up chloride ion from aqueous solution. Adsorption of chloride by CHT-X was investigated in batch mode. The kinetics study showed that the pseudo-second-order kinetics model could be used to describe the adsorption process satisfactorily. The equilibrium isotherm showed that the Langmuir model gave a better fit to the experimental data than the Freundlich model. The maximum adsorption capacity of CHT-3 was 83.33 mg/g; CHT-4 was 90.09 mg/g .The samples of different Mg/Al ratio have different crystallite size, thus showing different adsorption capacity. As the Mg/Al ratio increases from 3 to 4; the electric charge density between the layers becomes weaker; the interlayer spacing increases; the sample shows greater adsorption capacity. The HT-X where characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX).